Smoothing choke

ABSTRACT

This invention concerns a smoothing choke of a highly reduced weight. The smoothing choke consists of a magnetic core made up of a stock of trapezoidal metal sheets having the two parallel sides thereof alternately reversed so as to obtain a core of general parallepipedal shape having, at each end thereof, a groove in the shape of a triangular prism. A coil is wound around the core and has outer turns the perimeter of which is successively reduced by step-like winding, from the turns around the central part of the core, symmetrically, to the turns around the ends of the latter.

United States Patent [191 Bingen et al.

[ Jan. 8, 1974 SMOOTHING CHOKE [75] lnventors: Roald Bingen, Marcinelle;Jacques Van Hulse, De Pinte, both of Belgium [73] Assignee: ACECCateliers DE Constructions Electriques de Charierol, Cl arleroi, Belgium22 Filed: Feb. 26, 1973 211 Appl. No.: 335,930

[30] Foreign Application Priority Data Feb. 25, 1972 Belgium P 3822 Mar.7, 1972 Belgium .l P 3823 [52] US. Cl 336/59, 336/225, 336/231, 336/234[5 l] Int. Cl. H0lf 27/02 [58] Field of Search 336/60, 84, 233, 336/234,225, 231, 221,59

[56] References Cited UNITED STATES PATENTS 1,260,743 3/l9l8 Attila336/234 X I I v McCord 336/234 X Reade 336/234 X FOREIGN PATENTS ORAPPLICATIONS 254,616 1/1963 Australia 336/225 Primary Examiner-Thomas J.Kozma Att0rneyRaymond A. Robic [57] ABSTRACT This invention concerns asmoothing choke of a highly reduced weight. The smoothing choke consistsof a magnetic core made up of a stock of trapezoidal metal sheets havingthe two parallel sides thereof alternately reversed so as to obtain acore of general parallepipedal shape having, at each end thereof, agroove in the shape of a triangular prism. A coil is wound around thecore and has outer turns the perimeter of which is successively reducedby step-like winding, from the turns around the central part of thecore, symmetrically, to the turns around the ends of the latter.

10 Claims, 2 Drawing Figures PATENTEUJAN W 3.784.946

.m-H 1. [if 2 FIG.1

PATENTEDJAN 4 3,784,946

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SMOOTHING CHOKE The present invention relates to self-induction coilswith open-magnetic circuit and, in particular, to smoothing chokesuseful in current regulating electronic apparatus for regulating thefeed-current of impulse working traction motors.

The invention concerns a smoothing choke, of highly reduced weight,which is most important for an apparatus set up in a vehicle.

According to the invention, a first means for obtaining a substantialreduction in the weight of a coil of this type consists in using amagnetic core made up of a stack of trapezoidal metallic sheets the twoparallel sides of which are alternatively reversed so as to obtain acore of a generally parallelepiped form having, at each end, a groove inthe shape of a triangular prism. As it has been observed, these groovesdo not substantially change the induction coefficient of a coil placedaround the core as compared to the coefficient that would be obtained ifthe core were a complete rectangular parallelepiped.

It has been noted, on the other hand, that with this type of core thelines of force of the magnetic field produced by the coil are muchcloser to the core at its ends than if the latter were a rectangularparallelepiped of the same external size. In accordance with theinvention, advantage is taken of this characteristic by distributing thewinding along the height of the core so that the perimeter of the outerturns be successively reduced from the ones around the central part ofthe core to the ones around the ends of the same. In this manner, thearea defined by each outer turn is best adapted to the flux through itand a substantial reduction in the length of the average turn isobtained when compared with a coil containing the same number of turnsof the same cross-section of which the outer turns have all the samewidth. As a result, a substantial reduction in the weight of copper isobtained which may be improved some more due to the fact that the coilhas a greater external cooling area, which allows the use of a coilcontuctor having a smaller cross-section.

The invention will now be disclosed with reference to a preferredembodiment thereof, by way of example, and to the accompanying drawingsin which:

FIG. 1 is a perspective view of a core made up of a stack of metallicsheets in accordance with the invention;

FIG. 2 is an elevation view of a smoothing choke with the magnetic coreof FIG. 1.

FIG. 1 show a core made up of a stack of trapezoidal metal sheets 1 and2, alternatively disposed, the parallel sides of which are superimposed, the larger side of one fallowing the smaller side of the otherand vice versa; for the sake of clarity, these are shown separated fromone to the other. The sheets 1 and 2 are identical and made from a striphaving a width 1; the end edges of which are symetrically cut out at 45with respect to the parallel edges of the strip. In this manner, thereis obtained a magnetic core of a general parallelepipedal shape fromwhich a prismatic volume equal to l L/2 is cut off at each end, L beingthe thickness of the stack of sheets, so that the parallelepiped isreduced by a total volume of 1 L, which is, in general, quite animportant portion.

The production cost is also proportionally reduced because of the lesserweight of sheets used and of the bevelling thereof which avoids anyloss.

FIG. 2 is a cross-section view of a smoothing choke equiped with themagnetic core shown in FIG. 1. On this core, there is wound a coil 3 theturns of which are in step-like formation symmetrically on either sideof a central part with respect to a median plane which is perpendicularto the core so that the outer turns progressively get shorter as theymove away from the central portion.

It has been foun that such a coil has substantially the same inductioncoefficient as a coil having the same number of turns, such as shown indotted lines in FIG. 2, and for which the average length of a turn wouldbe greater, corresponding to a greater weight of copper. In as much asthe coil according to the invention has a larger outer cooling ares, thecross-section of the winding conductor may be reduced, which means anadditional reduction in the weight of copper used.

It can therefore be seen that the use of th disclosed magnetic core,which already has a reduced weight as compared to the parallelpiped coreof the same external size, allows the use of a coil having a weightsmaller than that of a known coil. Therefore, these combined featuresresult in a smoothing choke of a total weight clearly smaller than thatof known chokes of the same electrical characteristics.

The chokes shown in FIG. 2 may be secured by means of wedge-like member4 and 5 fitting into the prismatic grooves at the ends of the core andassembled by rods 6 secured to transverse members 7 and 8. The foregoingcombination is thus quite resistant to vibrations. I

The smoothing choke described above which has a stary field of littlescathering beyond the winding may be covered with a steel split housing,not shown, used as a magnetic screen and capable of acting as aventilation flue.

We claim 1. A smoothing choke comprising a magnetic core made up of astack of metal sheets having the two parallel sides thereof alternatelyreversed, said core having at each end thereof a groove in the form of atriangular prism; and

a coil wound around said magnetic core, the perimeter of the outer turnsof said coils being successively reduced, whereby a substantialreduction in the weight of said smoothing choke is obtained whencompared to the weight of known chokes.

2. A smoothing choke as claimed in claim 1 wherein each of said metalsheets is trapezoidal.

3. A smoothing choke as claimed in claim 2, wherein said metal sheetsare set up so as to obtain a core of general parallelepipedal shape.

4. A smoothing choke as claimed in claim 1 wherein said perimeter ofsaid outer turns is reduced by steplike winding.

5. A smoothing choke as claimed in claim 4 wherein the reduction in saidperimeter is from the turns around the central part of said core to theturns around each end thereof, symetrically.

6. A smoothing choke as claimed in claim 1, wherein the outer turns ofsaid coil progressively get shorter as said turns move away from thecentral portion of said core.

3 4 7. A smoothing choke as claimed in claim 1, wherein a magnetic coremade up of a stack of trapezoidal said core is fixed by means of V-shapeside parts fitting metal sheets having the two parallel sides thereofinto the prismatic grooves at the ends of said core and alternatelyreversed so as to obtain a core of genmeans holding said side parts andcoil together. eral parallelepipedic shape having, at each end 8. Asmoothing choke as claimed in claim 1, wherein 5 thereof, a groove inthe form of a triangular prism; said choke is secured by means ofwedge-like member a coil wound around said core and having outer turnsfitting into said prismatic grooves and assembled by the perimeter ofwhich in successively reduced, by means secured to transverse members.step-like winding from the turns around the central 9. A smoothing chokeas claimed in claim 1, wherein part of said core, symetrically, to theturns around said choke is covered with a split housing capable of 0 theends of said core, whereby a substantial reducacting as a magneticscreen for the stray field of said tion in the weight of said choke isobtained when choke and as a ventilation flue. compared to the weight ofknown chokes.

10. A smoothing choke comprising:

1. A smoothing choke comprising : a magnetic core made up of a stack ofmetal sheets having the two parallel sides thereof alternately reversed,said core having at each end thereof a groove in the form of atriangular prism; and a coil wound around said magnetic core, theperimeter of the outer turns of said coils being successively reduced,whereby a substantial reduction in the weight of said smoothing choke isobtained when compared to the weight of known chokes.
 2. A smoothingchoke as claimed in claim 1 wherein each of said metal sheets istrapezoidal.
 3. A smoothing choke as claimed in claim 2, wherein saidmetal sheets are set up so as to obtain a core of generalparallelepipedal shape.
 4. A smoothing choke as claimed in claim 1wherein said perimeter of said outer turns is reduced by step-likewinding.
 5. A smoothing choke as claimed in claim 4 wherein thereduction in said perimeter is from the turns around the central part ofsaid core to the turns around each end thereof, symetrically.
 6. Asmoothing choke as claimed in claim 1, wherein the outer turns of saidcoil progressively get shorter as said turns move away from the centralportion of said core.
 7. A smoothing choke as claimed in claim 1,wherein said core is fixed by means of V-shape side parts fitting intothe prismatic grooves at the ends of said core and means holding saidside parts and coil together.
 8. A smoothing choke as claimed in claim1, wherein said choke is secured by means of wedge-like member fittinginto said prismatic grooves and assembled by means secured to traNsversemembers.
 9. A smoothing choke as claimed in claim 1, wherein said chokeis covered with a split housing capable of acting as a magnetic screenfor the stray field of said choke and as a ventilation flue.
 10. Asmoothing choke comprising: a magnetic core made up of a stack oftrapezoidal metal sheets having the two parallel sides thereofalternately reversed so as to obtain a core of general parallelepipedicshape having, at each end thereof, a groove in the form of a triangularprism; a coil wound around said core and having outer turns theperimeter of which in successively reduced, by step-like winding fromthe turns around the central part of said core, symetrically, to theturns around the ends of said core, whereby a substantial reduction inthe weight of said choke is obtained when compared to the weight ofknown chokes.